1. Field of the Invention
The present invention relates to a water-cooled internal combustion engine having a radiator through which cooling water circulates from water jackets provided in a cylinder block and a cylinder head included in an engine body.
2. Description of Background Art
A cooling device for an internal combustion engine is known wherein a radiator through which the cooling water circulates from water jackets provided in an engine including a cylinder block and a cylinder head. The cooling device is disposed and is separated from the engine body in a prescribed direction. A supply pipe is connected to the cylinder block for supplying the low-temperature cooling water pressure fed by a water pump after radiating heat at the radiator to the water jackets. An inlet pipe for leading the cooling water coming from the water jackets after cooling the cylinder block and the cylinder head to the radiator is connected to the cylinder block. See, for example, JP-A No. 2005-9499.
In an internal combustion engine in which a supply pipe and an inlet pipe are connected to a cylinder block, the cylinder block is required to be provided with a return water path for returning the cooling water flowing out of the cylinder block into a cylinder head for thereby cooling the cylinder head back to the cylinder block. This complicates the cooling water circulation structure of the cylinder block and enlarges the cylinder block so as to accommodate the return water path. If, in such a case, a thermostat is to be installed in the cylinder block, the cooling water circulation structure of the cylinder block is further complicated.
In an internal combustion engine in which an accommodation chamber for accommodating, for example, a transmission mechanism for rotationally driving the cam shaft of a valve train is disposed in an end portion toward a radiator of the engine body. The accommodation chamber is positioned between water jackets and the radiator. As a result, the distance in a prescribed direction between the radiator and the water jackets, all separated from the engine body in the prescribed direction, is lengthened by an amount equivalent to the length in the prescribed direction of the accommodation chamber. This results in longer cooling water piping connecting the engine body and the radiator, making it difficult to compactly lay out the cooling water piping.
In cases in which a temperature sensor for detecting the temperature of the water jacket cooling water is used to detect the engine temperature, it is preferable for the purpose of detecting the temperature of the engine body as a whole that the temperature sensor should be disposed in a location that is not much affected by local water temperature changes in the water jackets. Furthermore, the disposition of the temperature sensor preferably should not prevent the cooling water piping from being compactly laid out.
Still furthermore, in cases in which an air vent pipe for letting out air inside a water pump is connected to the radiator, the air vent pipe is lengthened to result in restricting the layout of other cooling water pipes. This complicates the layout of the cooling water piping.